The invention relates to a pair of pliers with an arresting device for the arresting thereof in a clamping position.
The term pliers is hereby to be understood in the broadest sense and should thus not only include so-called clamping pliers in which, upon movement of the lever handles towards each other, the jaws of the pliers move toward each other and clamp an object therebetween, but also so-called spreading pliers in which the movement of the lever handles towards each other is transformed into a spreading apart of the jaws of the pliers. Typical pliers of the last-mentioned type are, by way of example, the speculae used for medical purposes, and which serve for widening body openings for examinations and operations.
In both cases the arresting device serves for arresting the pair of pliers in the momentary spreading position, which corresponds with the desired or required clamping pressure of the jaws inwardly or outwardly.
A speculum for gynaecological examinations is known, in which the arresting member is formed by a pin with a flat, for example, oval or rectangular cross-section, which at the narrow edges thereof is provided with thread-type ribs. This pin is rotatably fastened about its lengthwise axis at the one lever handle of the speculum and projects perpendicularly away from this one lever handle toward the other lever handle. The pin penetrates with its free end through an elongate slot in said other lever handle. The opening width of this slot is larger than the pin body, yet smaller than the extent of the pin including the ribs thereof. If therefore the pin is in a rotational position in which the ribs of the pin are directed against the ends of said slot, the lever handles can be freely moved towards each other or spread apart from one another, whereby the pin slides in the slot in accordance with the momentary spreading position of the lever handles and that concerns not only the extent of penetration but also the position of the pin within the lengthwise extent of the slot. When the desired clamping position is reached, this position can be arrested by turning the pin through 90.degree. in that namely the lengthwise edges of the slot are caught in each case between two adjacent ribs of the pin on the opposite narrow sides thereof and every further forward or backward sliding of the pin in the slot is prevented. To release this arresting action, it is then sufficient to rotate the arresting pin about the lengthwise axis thereof until the ribs withdraw from the region of the edges of the slot, whereby the arresting action is eliminated and the arresting pin can freely slide in the slot. Consequently, the lever handles can be moved without hindrance.
The advantage of this previously known pair of pliers, is namely that it can be frequently used because the arresting action wears out only slowly, but on the other hand these pliers are associated with the disadvantage that the user needs both hands for the arresting action, namely one hand to clamp the pair of pliers by means of the lever handles and to hold the pair of pliers in the desired clamping position and the other hand to rotate the arresting pin in the last-mentioned clamping position and to lock the clamping position.
In pliers of the known type for medical usage, the aforementioned advantage is attained at the expense that the pair of pliers is fabricated from a sterilizable material. Nowadays however, the trend is, as is already the case with syringes, towards instruments which are provided only for one-time usage, so that the mentioned advantage has appreciably lost significance at least as concerns pliers for medical usage.